Telecommunication equipment installations customarily employ electronic hardware racks, respective shelves of which have backplane connectors into which printed circuit boards are inserted. For this purpose, a typical housing architecture may contain mutually aligned sets of elongated U-shaped card guides that are affixed to upper and lower frames of the shelf. These card guides are sized to receive and guide upper and lower edges of printed circuit boards into physical and electrical engagement with backplane connectors, that are vertically installed in a side-by-side arrangement at a backplane of the shelf. The front edge of each printed circuit board is usually terminated by a face plate, having a latch that engages the shelf frame, when the printed circuit board is fully inserted into its slot, so that the front plates of multilayer printed circuit board forms a front panel closure for the shelf.
With such a compact and nested arrangement these are two operational issues that must be addressed: providing sufficient air flow over the printed circuit boards for cooling; and constraining electromagnetic interference (EMI). To constrain EMI emissions, the shelf is customarily surrounded by conductive (metallic) shielding plates, two of which serve as upper and lower mounting supports for the mutually aligned sets of card guides. In order to provide air flow to the printed circuit boards, a plurality (e.g. matrix) of holes or perforations may be formed in each mounting plate.
Unfortunately, this configuration suffers from several drawbacks. First, in order to support the card guides, the perforated mounting plates must have sufficient thickness for rigidity and strength. Secondly, because of the presence of the card guides, relatively large air flow apertures must be formed in the mounting plates between the card insertion channels in order to afford adequate air flow to the cards. However, since large air flow apertures undesirably provide a path for EMI emissions, it is necessary to install additional perforated EMI shielding plates adjacent to the card guide mounting plates. Such additional shielding plates undesirably increase hardware volume, complexity and cost, especially since a different tooling set is required for each type of shelf arrangement.